The problem of coupling a rotating element to a non-rotating element while permitting a fluid to pass from one element to the other without leakage has been a challenging engineering problem for many years. The problem is amplified when high temperatures or high process fluid pressures are encountered.
Numerous solutions to this fundamental engineering problem have been proposed over the years and many rotary joints, couplings or seals have been invented and utilized in industry.
Calender rolls operating at high speeds, high temperatures and high pressures for pressing paper in pulp and paper mills present a problem of this nature together with other problems. Heating water is passed through the calender rolls at pressures up to 300 psi and at temperatures up to 450 deg. F. The calender rolls rotate at high speed pressing and ironing the continuous paper sheet that passes between the rolls. Lumps are often present in the paper sheet and cause the rolls to separate suddenly and impact together suddenly. This causes shock waves to be generated and transmitted to the rolls and any equipment attached to the rolls. The pipes transmitting heating fluid to and from the calender rolls are stationary. Many designs of rotary joints or couplings have been developed over the years for the purpose of connecting the stationary pipes to the rapidly rotating calender rolls, while conducting heating fluid through the calender rolls. Notwithstanding the technology that has been developed in this area over the years, it is common for such rotary joints or couplings to begin to leak two to three months after installation from seal breakage due to shock transmission. In the higher temperature cases, the bearings in the rotary joints seize from seal breakage that occurs due to impact shock. The bearings on the rotary joints must then be replaced.
A number of patents disclose rotary couplings or joints which are representative.
U.S. Pat. No. 3,833,273, Rickley et al., granted Sept. 3, 1974, discloses, in a rolling mill, an interlocking labyrinth-type seal for a roll neck which is rotatably supported in a chock assembly. The seal includes an inner first sealing element which rotates with the roll neck, an outer second sealing element which is fixed in relation to the chock assembly, and a third sealing element which is carried on and movable axially along one or the other of the first or second sealing elements. The sealing elements have axially and/or radially spaced flanges and surfaces which cooperate to define an interlocking sealing labyrinth for preventing the escape of lubricating oil from the bearing, while at the same time preventing the bearing and lubricating oil from becoming contaminated with rolling lubricant cooling water, mill scale, dirt, and the like.
U.S. Pat. No. 4,071,255, Salter, Jr., granted Jan. 31, 1978, discloses a flexible seal element with a reinforced drain labyrinth for use on the outer seal ring of a seal assembly located between a roll end face and a bearing chock in a rolling mill, particularly the bearing chocks of the upper backup roll and the work rolls in a four-high mill. The seal element has a circular body portion adapted to tightly surround the outer seal ring. A first circular lip extends outwardly away from the body portion at an angle relative to the axis thereof to frictionally contact the roll end face. The seal body has a drain opening which is arranged to be aligned radially with a drainage port in the outer seal ring. The drain opening is protected by a second lip which extends outwardly from the seal body in a direction opposite to that of the first mentioned lip. A relatively stiff baffle member is attached to the seal body at a location spaced radially inwardly from the second lip. The baffle member and the second lip cooperate in providing a reinforced drain labyrinth which effectively prevents cooling water, mill scale, and the like, from being centrifugally directed upwardly into the bearing from the rotating surfaces of underlying rolls.
U.S. Pat. No. 4,585,236, Divirgilio, granted Apr. 29, 1986, discloses a circular coolant seal which has a base flange arranged in a base plane perpendicular to the seal axis. A flexible resilient sealing flange is integrally joined at one edge to the base flange and terminated at its opposite edge in a sealing lip located in a sealing plane parallel to and spaced axially from the base plane. The sealing lip has a first portion extending from the base flange angularly away from the base plane and inwardly towards the seal axis to an intermediate hinge portion, and a second portion extending from the hinge portion away from the seal axis and angularly towards the sealing plane. The configuration, flexibility and resilience of the sealing flange is such that axial displacement of the sealing lip in relation to the base flange is accompanied by both axial and radial displacement of the hinge portion.
U.S. Pat. No. 3,167,332, Simmers, granted Jan. 26, 1965, discloses an apparatus for cooling trunnions and bearings for converters in steel mills wherein a large quantity of heat is generated. The device is specifically directed to cooling a trunnion, its journal and bearing, which has no readily accessible open end to which a conventional cooling system may be attached.
U.S. Pat. No. 3,259,442, Boghosian, granted July 5, 1966, discloses a seal for use in a rolling mill and more particularly to a means of preventing contamination of roll neck bearings by foreign matter such as cooling water, mill scale, dust, and the like, while at the same time, preventing loss of lubricating oil from the bearing chocks.